Method of producing composite bushings

ABSTRACT

In a process of making bearings of lead bronze a large steel cylinder is lined on the inside thereof with a layer of lead bronze, said layer being produced by centrifugal casting. The steel cylinder and its lining layer are then cut to separate pieces along generatrices of the former and of the latter, and composite bearings are formed of these separate pieces.

United States atent Timmermans METHOD OF PRODUCING COMPOSITE BUSHINGS[72] Inventor: Frans Donatus Timmermans, 23 Kiel Brunswiker Str. 11a,Kiel, Germany [22] Filed: Oct. 11, 1968 [21] Appl. No.1 767,589

[52] U.S. Cl. ..29/149.5, 29/l49.5 S, 29/527.6, 29/527.7 [5l] Int. Cl...B21d 53/10, 823p 1 1 /00 [58] Field of Search ..29/149.5, 527.6,527.7, 149.5 D, 29/l49.5 Q, 149.5 S, 149.5 C

[56] References Cited UNITED STATES PATENTS 2,106,590 1/1938 Boegeholdet al. ..29/527. 6

2,289,703 7/1942 Goerke et al. ..29/149 5 2,503,533 4/1950 Williams2,971,248 2/1961 Kingsley et al.

3,500,526 3/1970 Taft 2,384,654 9/1945 Smith ..29/149.5 R

Primary ExaminerThomas H. Eager Attorney-Erwin Salzer 57] ABSTRACT In aprocess of making bearings of lead bronze a large steel cylinder islined on the inside thereof with a layer of lead bronze, said layerbeing produced by centrifugal casting. The steel cylinder and its lininglayer are then cut to separate pieces along generatrices of the formerand of the latter, and composite bearings are formed of these separatepieces.

9 Claims, 8 Drawing Figures PATENTEBAPR 4 I572 3,653,109

D. Tlmmermons F e 0 By [OX/WW Afly.

- Q INVENTOR: I;

BACKGROUND OF THE INVENTION As is apparent from the above the presentinvention relates to a method of making composite bearings of steel andlead bronze, or similar material.

Composite bearings are often made by so-called strip lining. This methodis especially applied if the steel jacket, or backing, of the bearinghas only a thin or medium wall thickness of, for example, 1 to 6 mm.This method includes the step of continuously casting a lining of leadbronze upon a steel strip moving forward horizontally at a speeddepending upon the downilow of molten lead bronze.

There is another known method of making composite bearings, the socalledroll" method, a centrifugal method in which tubular sections of steel ofa diameter equal to that of the bearings to be made, but several timestheir width, that is, in lengths of about 200 to 400 mm., are lined bycentrifugal action and then divided into individual rings each havingthe desired width of the bearings.

The strip lining method allows economical mass-production; however, ithas a drawback which relates to the bonding of the lead bronze layer tosteel, which drawback has not yet been overcome. The roll method, on theother hand, is not economical for making thin walled bearings on a largescale.

Another known method of making composite bearings includes the step ofcentrifugally lining a cylinder or tubular section of sheet steel whichhas a very large diameter and such a length that it may be divided intoa large number of bearing rings, or bearing sections which aresubsequently shaped into half shells. The sheet steel cylinder has suchdimensions that it retains its shape in spite of high temperatures ofabout 1,100 C. The wall thickness of the steel cylinder is, therefore,made so large that deformations on account of its thickness are avoided.This, in turn, requires that the steel backing must thereafter be turneddown on a lathe. It is quite evident that this method is veryuneconomical.

An improvement of this method has been predicated upon neglectingstrains and dislocations. This method involves inserting the deformedcylinder into a die which consists of a strong cylinder which issubdivided into a plurality of segments having an outer diametercorresponding to the inner diameter of the deformed cylinder.Furthermore the deformed cylinder may be inserted into another die,working as a counterpart, clamping the deformed cylinder on the wholecircumference from the outside. It has been expected that by turning outthe inside of the cylinder clamped in such a fashion and then grindingits outside while clamped from the inside, the deformed cylinder, afterhaving undergone this procedure, might show all over an equal thicknessof its lead bronze layer as well as of its steel layer. But this isactually not the case.

It is, therefore, an object of the present invention to provide a newmethod of making composite bearings which method constitutes animportant improvement of the centrifugal casting method previouslydescribed, inasmuch as the bonding of the lining metal to the steelbacking effected by the centrifugal action is more efiective than can beachieved by means of the prior art stripping method. Furthermore, thenovel method achieves an even thickness of the lining as well as of thesteel backing and is not less economical than the well-known strippingmethod, and much superior to the prior art centrifugal casting methods.The method according to the present invention is related to the priorart centrifugal method inasmuch as it also utilizes a steel cylinderlined by centrifugal action with lead bronze. The steel cylinder has alength, or height, and a circumference, or diameter, which are manytimes of those of the bearings made. Such a steel cylinder is lined bycentrifugal action on the inside with a layer of lead bronze, or similarmaterial. The subsequent steps of the method according to this inventionare different from any prior art method. This will become more apparentfrom the following description and from the accompanying drawings.

SUMMARY OF THE INVENTION The process according to this inventionincludes the step of lining a steel cylinder whose diameter is largerthan the diameter of the hearings to be made on the inner surfacethereof with a lining of lead bronze by means of centrifugal action, orcentrifugal casting. Thereupon the cylinder is subdivided along thegeneratrices thereof into a plurality of workpieces which are firstflattened and then pressed into shape to form bearing shells. There aretwo principal ways of achieving this end. Either the cylinder may be cutopen along one single generatrix thereof and thereafter converted into,or rolled to form, a flat plate. The latter is subsequently cut intostrips from which bearings are formed. As an alternative, the cylindermay be cut initially into a plurality of sections along a plurality ofgeneratrices thereof, which sections are then formed into bearings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a steelcylinder having an internal lining of lead bronze;

FIG. 2 is an isometric view of the same cylinder as shown in FIG. 1 andFIG. 2 indicates a plurality of generatrices along which the cylinder isto be subdivided to form a plurality of workpieces in the form ofstrips;

FIG. 3 is a diagrammatic side elevation of a bending device, or die, forbending strips resulting from subdividing the cylinder of FIGS. 1 and 2along generatrices thereof in a direction transversely to their initialcurvature;

FIG. 4 is a side elevation of a strip resulting from subdivision of thecylinder of FIGS. 1 and 2 and subsequent bending of the strip in thebending device of FIG. 3 to form a bearing halfshell;

FIG. 5 is an isometric view of the same cylinder as shown in FIG. 1 uponbeing cut open along a generatrix thereof and in the process of beingunrolled into a plane;

FIG. 6 is a diagrammatic side elevation of a roller press for flatteningthe cylinder sections resulting from the subdivision of a cylindricalsurface such as shown in FIGS. 1 and 2;

FIG. 7 is a diagrammatic side elevation of a rolling device forprocessing workpieces formed by subdividing a cylinder such as thatshown in FIGS. 1 and 2; and

FIG. 8 is a top plan view of a cutting device for severing a cylindricalsurface along generatrices thereof as indicated in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows an end view of alead-bronze-lined steel cylinder a. The thickness of itslead-bronze-lined steel sheet exceeds that of the finished bearing witha necessary minimum after cleaning as usual by means of the picklingbath. Corrosion during the lining process can be avoided by addinggraphite to the lead bronze chips, or molten material and by using aprotective gas such as hydrogen, or nitrogen, or the like. Thelead-bronze-lined cylinder may now be cut into strips in axial directionhaving substantially the width of the bearings (plus a small excess).

FIG. 2 shows the mode of dissecting the cylinder of FIG. 1 into strips mwhich process may be carried out by means of a machine such as thatshown in FIG. 8 in an end view. Referring now to FIG. 8, a is thelead-bronze-lined cylinder inserted into, and carried by, a clampmechanism n pivoted at a center. Part 1' forms a guide for cylinder a.Between i and I an adjustable slit is formed which receives the wall ofthe cylinder a. The clamp mechanism n supporting cylinder a moves theleft edge of the cylinder wall into the slit formed between parts i andI until it engages stop or dog 1. Then the wall of the cylinder at isstopped by the stop or dog j and is ready to be cut off by means of thechisel k. The chisel k cuts off rapidly one strip m after another, i.e.,at a high repetition rate. Strips m have a width corresponding to thatof the prospective bearing. The strips m are cut into shorter pieces,and these pieces have a length corresponding to the circumference of abearing half shell. The steel backing and the inner lining of leadbronze of these strips have a uniform wall thickness at all points. Thenthese sections of strips m still having a curvature in longitudinaldirection, may be pressed crosswise to the longitudinal curvature toform bearing half shells with an inside lead-bronze-lining as shown inFIG. 4.

According to FIG. 3 the die I) presses each strip-section m crosswise toits longitudinal sinuous cavity from the leadbronze-side into the hollowform c. This process involves a pressing action in two directions, i.e.,flattening of strip m in one direction and curving of the strip m to thebearing half shell in a crosswise direction. This is achieved whilepressing the strip m into the proper matrix c.

FIG. 4 shows a bearing half shell formed in that way in an end view. Bythis rather unorthodox way of crosswise pressing all deformations andtensions produced as a result of the centrifugal lining process of thecylinder disappear entirely, and the shell gains increased hardness.This kind of dual bending is one of the essential features of thepresent invention. One may subdivide the process of exerting pressurecrosswise upon the strips resulting from sub division of the linedcylinder into two steps. The first step includes rolling outlongitudinal strips to remove their initial cylindrical curvature andthe second step includes rolling of flattened strips in crosswisedirection. In order to do so one may cut the cylinder longitudinallyinto two portions one of which is the welding seam and the other therest of the cylinder. The cylindrical surface thus opened is flattenedby re-rolling. Thus its wall forms, in effect a substitute for a flatpiece of steel strip lined with lead bronze as produced by prior artmethods. The re-rolling process will, in general, flatten the cylinderwall only to a limited extent, i.e., there will not be significantelongation of the cylinder wall exceeding the order of 5 percent. Thisis enough to do away with any deformation and strain by cold steel-flow.The step of rolling of the lead-bronze-lining, coupled with theflattening of the concave surface, is quite unorthodox because of theprevalent erroneous belief that by rolling the concave surface of theleadbronze-lining the latter would break up, i.e., become incapable offorming a bearing surface. It is another part of the present inventionto have overcome this erroneous concept.

FIG. 5 shows the open cylinder a with its steel backing d and thelead-bronze-lining e viewed during the re-rolling process. THe flattenedlined steel strip may be rolled between two rollers as shown in FIG. 6to various degrees of elongation not exceeding 5 to percent of thelength of the flattened cylinder wall a with the steel backing d and thelining 2. FIG. 6 shows how layers a and e are rolled between the tworolls w and w.

FIG. 7 also shows a rolling process of flattened lead-bronzelined steelcylinders. Two pieces to be rolled jointly are inserted between the pairof rolls w. The pieces each including backing d and lining e are puttogether with their lining surfaces, the latter being separated bygraphite or the like intermediate layers preventing the pieces to fusetogether.

If it is intended to roll down heavy cylinder sections, cold rolling isno longer practicable. It is then necessary to resort to hot-rollingwhen rolling down the lead-bronzedined steel plates. The temperature atwhich this hot-rolling process must be performed depends upon thecontents of lead in the lead bronze, i.e., the proportion of lead tocopper. This may be, for instance, l5 percent or percent. Therollability of leadbronze-lined steel decreases as the contents of leadin he lead bronze increases. A relatively thick lead-bronze-lined steelplate calls for red-heat temperatures for its rolling process. At suchtemperatures the lead phase in the lead bronze melts but is notsignificantly squeezed out of the sandwich, even in the presence ofheavy rolling pressures.

Instead of feeding two superimposed lead-bronze-lined plates to the nipformed between rollers w as shown in FIG. 7, a non-lined heavy steelplate may be substituted for one of the lead-bronze-lined plates. Such aheavy steel plate should be much heavier than the lead-bronze-linedsteel plate, exceed the length and the width of the latter and used incold condition.

As mentioned above, an appropriate separator ought to be insertedbetween pairs of plates which are being jointly rolled. The hot-rolledlead-bronze-lined plate may be subsequently re-rolled in cold conditionin order to harden the steel backing thereof.

Another aspect of the invention relates to the cooling of the workpiecesand the heating thereof. The preferred method of heating the rotatingcylinder to line the same with lead bronze is induction heating. Theheating temperature may be in the order of 1,100 C. The inductive heaterincludes a spool or winding having but a few turns. This spool orwinding may be of copper and have fine perforations or holes allowingthe outflow of a cooling medium, such as water, upon the white-hot(1,100 C.) rotating steel cylinder. The evolving steam results indelayed cooling of the rotating steel cylinder. The still rotatingcylinder and the induction coil may be separated from each other and theformer may be dipped in part into molten lead, or into an alloy, havinga still lower melting point. This causes rapid cooling of the cylinder.Water may be used to achieve an additional cooling action. The rate ofcooling controls the time when solidification occurs, precludingseparation of the constituents of the lead-bronze.

The induction coil having few turns used for induction heating of thesteel cylinder to be lined with lead bronze may be cylindrical andinclude two semi-cylindrical sections which are pivotally interconnectedby hinge means including a shaft or pin of insulating material. Theinsulating material must by heat resistant or have a high melting point.The plastic material known by its trademark TEFLON may be used formaking the hinge pins. The electric contact or current-carryingconnection between the two semi-cylindrical sections of the inductionheating coil may be established by the aforementioned hinge means forpivotally attaching one of the sections to the other. In the systemunder consideration the induction coil for heating the steel cylinder tobe lined and the steel cylinder to be lined are arranged in coaxialrelation, their common axis being horizontal. After inductive heating ofthe steel cylinder in the process of being lined with lead-bronze up toabout 1,100 C., the induction coil is opened, i.e., its semiclyindricalsections pivoted apart, and moved upward. A container with molten leador alloy is likewise moved upward, or elevated. As a result, the lattercontainer surrounds the whitehot rotating steel cylinder and the moltenlead filling of the aforementioned container touches the steel cylinderwhose rotary motion is maintained. During this dipping process, which isin effect a controlled cooling processthe cooling medium being liquidlead or the like-the aforementioned container is covered so that noliquid lead can be thrown out of it. Upon completion of this coolingprocess the steel cylinder is moved back to its first or initialposition. Thereupon the split induction heater coil which has beenpreviously opened is reclosed, re-establishing a current path and awater channel through the constituent turns thereof. NOw the inductionheater is ready for pouring water upon the steel cylinder still inrotation.

The steel cylinder may have any desired diameter and any desired width.It is desirable to increase its diameter close to practical limits. Suchan increase of diameter imposes restrictions in regard to the width ofthe steel cylinder, i.e., its width must then be kept relatively smallin order to preclude a deformation or distortion of the steel cylinderby centrifugal action. The diameter of the steel cylinder may, forinstance, be cm. and the width of the cylinder wall 20 cm. or 25 cm.Such dimensions will result in a strip of lead-bronze-lined steel havinga length of about 4 in. after rerolling. Such a strip is then cut in adirection longitudinally thereof into two parts which are then used toform bearing half shells as shown in FIG. 4.

It is desirable to completely automate the production oflead-bronze-lined steel cylinders in accordance with a strict program.The timing of such an automated production set-up may be controlled bythermal sensing means, e.g., a pyrometer or spectrometer.

Summarizing the above, it will be apparent that the present method ofmaking composite bearings includes the step of lining a steel cylinderwith lead bronze by centrifugal action. This steel cylinder hasrelatively large dimensions as compared to the dimensions of theindividual bearings intended to be made, i.e., the diameter and also thelength of this steel cylinder exceeds the diameter and the length of theindividual bearings intended to be made. The wall thickness of the steelcylinder exceeds slightly the thickness of a backing layer of steel ofthe individual bearings intended to be made. The lead-bronzelined steelcylinder is cut open in axial direction and more or less flattened, orbent open by a rolling operation. The resulting lead-bronze-lined steelplate is cut along lines forming generatrices of the original steelcylinder into a plurality of strips. These strips are bent transverselyto the original curvature of the lead-bronze-lined steel cylinder toform the half shells of 180 shown in FIG, 4.

An important feature of this invention is flattening the stripsresulting from sectionalizing the surface of the lead-bronzelined steelcylinder in a direction longitudinally of said strips and of bendingthese strips transversely to form half cylindrical shells and to performthe flattening and transverse bending operation by one single stroke ofa pressure exerting die, as also shown in FIG. 4.

Another important feature of this invention is the removal ofdeformations and strains caused by the centrifugal lining process in thewalls of the steel cylinder by subjecting the walls to a rolling processfollowing slicing of the steel cylinder to increase the length thereofup to percent of its original length.

Hot-rolling is indicated and may be combined with coldrolling whereverrelatively heavy workpieces are involved.

An important step involved in the centrifugal casting or steel-cylinderlining process consists in continuously filling the closed steelcylinder with a suitable gas such as, for instance, nitrogen to protectthe melted lead bronze inside of the steel cylinder. The melted leadbronze may also be protected against oxidation by a mixture containinggraphite and a nitrogen compound evolving nitrogen at the hightemperaturesabout 1,100 C.involved in the centrifugal casting process.

Still another important aspect of the invention is the dual striprolling process illustrated in FIG. 7. In that modification of theinvention a pair of cut open lined steel cylinders is jointly rolleddown at elevated temperatures of about 500 C., or when red-hot. Bothlined flattened cylinder walls are superimposed with theirlead-bronze-linings in juxtaposition. The juxtaposed lead-bronze-liningsare separated by a sheet material during their joint and simultaneousrolling down process to preclude fusing together of thelead-bronze-linings thereof.

Having thus fully disclosed my invention, what I claim is:

1. A method of making composite bearings including the steps of lining asteel cylinder having relatively large dimensions as compared to thedimensions of the individual bearings to be made and having a length anda diameter far exceeding the length having a wall thickness but slightlyexceeding the wall thickness of a steel backing layer of said individualbearings with lead bronze by means of a centrifugal casting process,thereafter cutting said lead bronze lined steel cylinder in axialdirection thereafter flattening said lead bronze lined steel cylinderand bending it open by a rolling operation, then cutting the flattenedlead bronze linedsteel plate thus obtained along generatrices of saidsteel cylinder into a plurality of fiat strips, and bending saidplurality of flat strips transversely to the original curvature of saidsteel cylinder to form half shells of 2. A method of making compositebearings of steel and lead bronze including the steps of lining a steelcylinder having relatively large dimensions in comparison to thedimensions of the individual bearings to be made and having a length anda diameter far exceeding the length and diameter of said individualbearings and having a wall thickness exceeding the wall thickness of asteel backing layer of said individual bearinfgls only to a small extentwith lead bronze b3! means of a centri gal casting process, then cuttingthe line cylinder in axial direction into strips having a length equalto the height of said cylinder and a width equal to the width of saidbearings when finished, then cutting said strips to shorter lengthsubstantially equal to half the circumference of the bearings to bemade, then applying pressure to the shortened slightly curved strips toflatten said strips in a direction longitudinally thereof and bendingsaid strips transversely to form half cylindrical shells, saidflattening of each of said strips and said transverse bending of each ofsaid strips being performed by one single stroke of a pressure exertingdie.

3. A method of making a material for composite bearings of steel andlead bronze or similar material including the steps of lining a steelcylinder having relative large dimensions in comparison to thedimensions of individual bearings to be made by means of a centrifugalcasting process, thereafter cutting open the lined cylinder in an axialdirection and flattening the cylinder wall by slight rolling to resultin an increase in the length thereof up to 10 percent of the originallength of said cylinder, whereby deformations and strains caused by saidcentrifugal casting process in the walls of said steel cylinder areremoved.

4. A method as specified in claim 3 wherein the diameter of the linedsteel cylinder is in the order or in excess of 1 meter.

5. A method as specified in claim 3 including the step of protecting themolten lead bronze in the steel cylinder during the centrifugal castingprocess by continuously filling the closed steel cylinder with aprotective gas.

6. A method as specified in claim 5 including the step of protecting themolten lead bronze against oxidation by addition of a mixture containinggraphite and a nitrogen compound evolving nitrogen at the hightemperatures involved in said centrifugal casting process.

7. A method as specified in claim 3 including repeated rolling of saidcut opened lined cylinder for strengthening the same and to increase thelengthening effect of the initial rolling step.

8. A method as specified in claim 3 including the steps of jointlyrolling down a pair of said cut open lined flattened steel cylinders atelevated temperatures, of superimposing said pair of lined flattenedsteel cylinders with the linings thereof in juxtaposition while in theprocess of bei g ggmlg rgllad down, and separating said linings by asheet mate ial interposed between said linings during the rolling downprocess of said flattened steel cylinders at elevated temperatures.

9. A process as specified in claim 3 including the step of subjectingthe flattened cylinder walls to a joint rolling action and heattreatment at red hot temperatures of about 5 00 C.

1. A method of making composite bearings including the steps of lining a steel cylinder having relatively large dimensions as compared to the dimensions of the individual bearings to be made and having a length and a diameter far exceeding the length and the diameter of said individual bearings and having a wall thickness but slightly exceeding the wall thickness of a steel backing layer of said individual bearings with lead bronze by means of a centrifugal casting process, thereafter cutting said lead bronze lined steel cylinder in axial direction thereafter flattening said lead bronze lined steel cylinder and bending it open by a rolling operation, then cutting the flattened lead bronze lined- steel plate thus obtained along generatrices of said steel cylinder into a plurality of flat strips, and bending said plurality of flat strips transversely to the original curvature of said steel cylinder to form half shells of 180*.
 2. A method of making composite bearings of steel and lead bronze including the steps of lining a steel cylinder having relatively large dimensions in comparison to the dimensions of the individual bearings to be made and having a length and a diameter far exceeding the length and diameter of said individual bearings and having a wall thickness exceeding the wall thickness of a steel backing layer of said individual bearings only to a small extent with lead bronze by means of a centrifugal casting process, then cutting the lined cylinder in axial direction into strips having a length equal to the height of said cylinder and a width equal to the width of said bearings when finished, then cutting said strips to shorter length substantially equal to half the circumference of the bearings to be made, then applying pressure to the shortened slightly curved strips to flatten said strips in a direction longitudinally thereof and bending said strips transversely to form half cylindrical shells, said flattening of each of said strips and said transverse bending of each of said strips being performed by one single stroke of a pressure exerting die.
 3. A method of making a material for composite bearings of steel and lead bronze or similar material including the steps of lining a steel cylinder having relative large dimensions in comparison to the dimensions of individual bearings to be made by means of a centrifugal casting process, thereafter cutting open the lined cylinder in an axial direction and flattening the cylinder wall by slight rolling to result in an increase in the length thereof up to 10 percent of the original length of said cylinder, whereby deformations and strains caused by said centrifugal casting process in tHe walls of said steel cylinder are removed.
 4. A method as specified in claim 3 wherein the diameter of the lined steel cylinder is in the order or in excess of 1 meter.
 5. A method as specified in claim 3 including the step of protecting the molten lead bronze in the steel cylinder during the centrifugal casting process by continuously filling the closed steel cylinder with a protective gas.
 6. A method as specified in claim 5 including the step of protecting the molten lead bronze against oxidation by addition of a mixture containing graphite and a nitrogen compound evolving nitrogen at the high temperatures involved in said centrifugal casting process.
 7. A method as specified in claim 3 including repeated rolling of said cut opened lined cylinder for strengthening the same and to increase the lengthening effect of the initial rolling step.
 8. A method as specified in claim 3 including the steps of jointly rolling down a pair of said cut open lined flattened steel cylinders at elevated temperatures, of superimposing said pair of lined flattened steel cylinders with the linings thereof in juxtaposition while in the process of being jointly rolled down, and separating said linings by a sheet material interposed between said linings during the rolling down process of said flattened steel cylinders at elevated temperatures.
 9. A process as specified in claim 3 including the step of subjecting the flattened cylinder walls to a joint rolling action and heat treatment at red hot temperatures of about 500* C. 